Yeesa Cheung (Sofiee Ng), born on a leap day, believes her birthday is squeezed between 28 February and 1 March in common years.

There she is greeted by two strangers, Ryan Ma (Chui Tien-you) and Yu Ka-chung (Terrance Lau), and finds her future self killed in a traffic accident.

[4] Yamano Hisaji, the coordinator of the collaborating producer company in Japan, was additionally cast to play the pivotal role of Kagawa Niro.

[4][5] The crash scene in Episode 9 was so complicated and expensive that, in order to ensure a smooth filming, Law and cinematographer Dino Wong found a visualiser to draw a storyboard, which is rare for a television series.

[7] Sofiee Ng worked with Steve Law on Margaret & David - Ex the Special Episode and Terrance Lau with Yellow Wong on Limited Education.

At ViuTV 2021, the channel's presentation show aired on 17 October 2020, a drama series titled 940920 was announced, alluding to the secret code between Yeesa and Ka-chung in Leap Day.